I won't tell you that you shouldn't be careful, because Imuran is a nasty drug. I've been on 250 mg for the last four months, and prior to that, 200 mg for three years. I'm also on 9Mg of Entocort, which has it's own issues. But I will tell you that for me, anyway, I never get sick, and for the last year, I was doing a fair amount of travel, including a trip to Mexico at the end of last year. I'm also around a four year old that brings home all the good stuff from pre-school, like coughs and sniffles.
I'm probably not the typical Imuran user, and overall, I've always been one to resist getting sick, despite that fact that I have Crohn's, but I wanted to share this with you because I don't think you need to go overboard... like Agent said, no need for the Howard Hughes Syndrome!
Gary